Polymerization reactor provided with coating that suppresses polymer deposit formation

ABSTRACT

In a process of polymerizing ethylenically unsaturated compounds by polymerization of ethylenically unsaturated monomers in the presence of a free radical-forming initiator system and customary protective colloids and/or emulsifiers and optional known additives in a reactor whose surfaces contact the reaction components, the improvement comprising providing the reactor surfaces with a coating that at least suppresses polymer deposit formation without effecting the color and quality of the polymer.

PRIOR APPLICATION

This appliction is a continuation of copending U.S. patent applicationSer. No. 829,396 filed Feb. 13, 1986, now abandoned, which is a divisionof U.S. patent application Ser. No. 700,627 filed Feb. 12, 1985, nowU.S. Pat. No. 4,661,569.

STATE OF THE ART

In the manufacture of polymers of ethylenically unsaturated monomers,especially vinyl chloride alone or with at least one other ethylenicallyunsaturated compound polymerizable therewith, preferably in an aqueousmedium with a free radical-forming initiation system in the presence ofa protective colloid and/or emulsifiers and optional customaryadditives, polymer deposits form on the surface of the polymerizationreactor during the polymerization. The deposit forms on the reactionvessel and the optional equipment present therein which contact thecomponents of the reaction mixture.

The deposited polymers can not be further processed and constitute wastematerial which are a hazard to the environment in the case of vinylchloride polymers due to the high amounts of residual monomer content inmost instances.

Moreover, part of the deposits often become detached from the saidsurfaces even during polymerization and adversely affect the quality ofthe desired polymer product since they give rise to pin-holes or "fisheyes" therein. Finally, such crusts impede the dissipation of the heatof polymerization through the reactor walls which entails longerreaction times, uncontrolled progress of the reaction and risk to theoperational reliability.

The removal of such wall deposits and crusts is therefore necessary andthis is usually effected by mechanical means, for example by sprayingthe emptied reaction vessel or autoclave with high pressure water suchas greater than 100 bars. In so doing, however, the wall deposits whichusually adhere firmly generally do not become completely detached, andthe remaining portions caused an increased formation of such crusts insubsequent polymerizations. For that reason, the reactor has to beopened after only a few batches and mechanically cleaned by hand whileobserving complicated safety precautions. Apart from the prolongedshut-down periods resulting therefrom and the risk to the environment,especially to the maintenance staff, for example from vinyl chlorideresidues, it is not possible to avoid damaging the vessel walls and thesurfaces of the equipment in such cleaning operations using a spatula.Again such rough areas also form a starting point for an increasedformation of crusts.

For a long time, therefore, attempts have been made to find possibleways of solving these problems by reducing or preventing the formationof polymer crusts during polymerization. For example, proposals havebeen made for the autoclave dome to be sprayed with water duringpolymerization, or for suitable water-soluble substances such asnitrites to be added to the polymerization liquor. However, theseprocesses are not entirely satisfactory and also give rise to problemswith liquid waste, for example.

The other course most often followed in the meantime is coating of theinner walls of the reaction apparatus with largely insoluble coveringsof organic compounds that contain polar groups such as dyestuffs such asnigrosine black, Sudan black B inter alia (cf., for example, BritishPat. No. 1,562,290), polycondensates such as polyimines, polyamines andpolyphenols which in some cases have been cross-linked with an aldehyde(cf., for example, WO-A-82/02555, U.S. Pat. No. 3,055,876).

The known coatings did not meet all the requirements, either becausethey dissolved and became detached too readily, causing discoloration ofthe product, or because their action was still unsatisfactory. Nor arethey yet universally applicable or also still exhibit undesiredretarding action on polymerization and changes in the polymers such ascoarsening of the grain, reduction of the thermal loading capacity orstability also appeared.

To avoid these difficulties, U.S. Pat. No. 4,143,097 and No. 4,256,854have already proposed coatings based on certain derivatives ofbenzthiazol-2-one-hydrazone which may optionally be fixed to the wallsby certain carrier materials. In this connection, it is also proposedthat cross-linking materials such as shellac or alkyd resins based on anisocyanate or phenol-aldehyde, and also based on an epoxide or anhydridebasis be used for fixing the active ingredients. However, it isimportant for the active ingredient preferably not to be bondedchemically and especially not by way of the hydrazone group which isessential therein, since otherwise the desired deposit-suppressingaction does not appear. For that reason, it is also recommended in thesepatents that a hardener having a higher cross-linking activity than theactive ingredient be added to the epoxide or anhydride system.

Apart from the fact that the active deposit-suppressing portion of theactive ingredient is suspended only physically in the deposit and,therefore, is relatively easily washed out, especially when emulsifiersare used, the ratio of the mixture of epoxide prepolymer/hardener/activeingredient has to be adhered to very strictly when manufacturing thecoatings and due to the very short pot-time, the reactive coating agentcan be stored only for a limited period.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a novel polymerizationprocess that is simple and reliable, that exhibits a good to very goodactivity against the formation of polymer deposits, that even in theuncross-linked state possesses good resistance to being washed out and,in the cross-linked state, even where polymerization mixtures having ahigh content of emulsifiers are involved, possesses a resistance betterthan that in the prior art, and that avoids the disadvantages of theprior art which have been discussed above.

These and other objects and advantages of the invention will becomeobvious from the following detailed description.

THE INVENTION

In the novel process of the invention of polymerizing ethylenicallyunsaturated compounds by polymerization of ethylenically unsaturatedmonomers in the presence of a free radical-forming initiator system andcustomary protective colloids and/or emulsifiers and optional knownadditives in a reactor whose surfaces contact the reaction components,the improvement comprises providing the reactor surfaces with a coatingthat at least suppresses polymer deposit formation, the coating beingcomprised of at least one compound of the formula ##STR1## optionallysubjected to a cross linking reaction wherein X is selected from thegroup consisting of --O--, --S--, and ##STR2## Y is selected from thegroup consisting of --CH₂ OR₆, ##STR3## R₁ is selected from the groupconsisting of R₂ --, ##STR4## and R₂ --SO₂ --, R₂ is selected from thegroup consisting of phenyl and naphthyl optionally substituted with atleast one R₃ and heterocycle optionally substituted with at least one R₃and derived by substitution of nitrogen, sulfur and/or oxygen atoms forat least one carbon of benzene, cyclopentadiene, indene, naphthalene ortheir partially or completely hydrogenated analogs, alkyl of 1 to 8carbon atoms containing at least one R₃, ##STR5## R₃ is selected fromthe group consisting of --OH, --SH, ##STR6## --COOH and --SO₃ H, the R₄'s being independently selected from the group consisting of hydrogenand alkyl of 1 to 4 carbon atoms, R₅ is selected from the groupconsisting of ##STR7## R₆ is selected from the group consisting of##STR8## and R₇ is selected from the group consisting of alkylene of 1to 8 carbon atoms optionally substituted with at least one alkyl of 1 to4 carbon atoms, phenylene and naphthylene having at least one R₃ and/orR₄ and ##STR9##

The preferred compounds to be used in the coating of the reactor havethe formula ##STR10## which can also be subjected to a cross-linkingreaction wherein X is --O-- or --NH--, Y is --CH₂ OR₆, R₆ is ##STR11##R₇ is phenylene or naphthylene optionally carrying at least one R₃and/or R₄ and alkylene of 1 to 4 carbon atoms or ##STR12##

The coating of the surfaces is preferably effected by applying thecompound of formula I or a mixture of such compounds in the form of asolution or dispersion in polar solvents that are preferably free ofamino, imino, amido or imido functional groups and that boil preferablyat not more than 120°, especially at not more than 100° C., preferablyat room temperature for example approximately between 10° and 30° C.and, optionally, subsequently heating it to remove the solvent, forpreferably 30-120 minutes at preferably 40-120, more preferably 40°-100°C. The said solutions or dispersions each comprise preferably from 1 to10% by weight of at least one compound of formula I. It has also beenfound advantageous in many cases to adjust the pH of the solution of thecompound(s) of formula I to values of from 7 to 12, preferably from 9 to12, optionally by the addition of alkali metal or alkaline earth metalhydroxide, for example sodium, calcium and potassium hydroxide solution.

There may be mentioned as especially suitable solvents propanone andbutan-2-one, butanol, n-propanol and isopropanol and especially ethanoland methanol, each of which may optionally be mixed with up toapproximately the same amount of water.

In a preferred embodiment, a mixture of at least one compound of formulaI and at least one compound of the formula ##STR13## wherein R₇ has theabove definition in a molar ratio of from 10:1 to 1:1, preferably from8:1 to 2:1, is applied to the surfaces to be coated, preferablyaccording to the above measures and conditions, and dried preferably atthe temperatures given above and, in so doing, simultaneouslycross-linking thereon.

The process of the invention can be applied to a large number ofmonomers that are polymerized according to a suspension, emulsion ormicro-suspension process in an aqueous medium or by mass-polymerization.Examples of such monomers are styrenes, acrylates and methacrylates,vinyl esters, vinyl halides and vinylidene halides and mixtures thereof.

The process of the invention is especially suitable, and thereforepreferred, for homo-, co- and graft polymerization of vinyl chloride(VC). Further examples of suitable monomers and, provided they arecopolymerizable with one another and/or with VC, comonomers are vinylesters of carboxylic acids of the formula RCOOH wherein R is hydrogen orstraight-chain or branched alkyl of 1 to 20 carbon atoms, for examplevinyl formate, n-butyrate, sec-butyrate, tert-butyrate or laurate orstearate or versatate (=vinyl esters of Versatic® acids, carboxylicacids manufactured by Koch's synthesis, cf. Rompps Chemie-Lexikon, 7thedition, 1977, page 3803), preferably vinyl acetate and vinylpropionate; alkyl ester of 1 to 18 carbon atoms of α,β-unsaturatedcarboxylic acids having 3 to 6 carbon atoms in the acyl radical, forexample methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl,tert-butyl crotonate or itaconate and preferably methacrylate andespecially acrylate; styrene; vinyl-toluene; vinyl fluoride and bromide;vinylidene halides such as vinylidene chloride and bromide; α-olefins,such as propylene and preferably ethylene; maleic and fumaric acid mono-and/or di-esters with saturated alcohols of 1 to 18 carbon atoms; vinylethers; (meth)-acrylonitrile; (meth)acrylamide; vinylsulfonic acid, andsalts thereof; acrylic acid, methacrylic acid, maleic acid, fumaricacid, maleic anhydride and mixtures of such compounds, the water-solublestrongly polar monomers being used mostly in small amounts forstabilizing the dispersion.

Suitable polymerization processes that can be modified by the inventionare known, for example, from the following printed specifications:EP-A-No. 590, No. 8775, No. 14 420, No. 17 986, No. 28 812, N. 32 724,No. 62 106, No. 76 511 and No. 78 043 and DE-A-No. 2,206,593, No.2,234,038, No. 2,629,880, No. 3,215,624 and No. 3,312,255.

Especially preferred is the manufacture of VC-homopolymers andVC-copolymers having up to 40% by weight, based on the total weight, ofthe comonomer units mentioned.

With regard to the initiator system which may consist of oil-soluble orwater-soluble peroxidic compounds optionally combined with reducingagents, and with regard to the protective colloids, emulsifiers andfurther customary additives, reference is made for the purposes ofcondensing the description to the printed specifications mentioned aboveand also, for example, to D'Alelio, Fundamental Principles ofPolymerization, New York/London, 1952 and Houben-Weyl, Methoden derorganischen Chemie, 4th edition, 1961 volume 14/1.

The compounds of formula I can be manufactured from diglycidyl ethers offormula II, by reaction with benzene or naphthalene derivatives havingat least two substituents selected from hydroxy, thiol, amino, sulfoxyland/or carboxyl groups (R₃) with a heterocycle that is derivedpreferably from benzene by substitution of one or two, especially one,ring carbon atom(s), preferably by nitrogen, and that is subsituted byat least one of the mentioned groups R₃, with straight-chain or branchedalkyl of 1 to 8, preferably 1 to 4, carbon atoms that is substituted byat least two of the mentioned groups R₃, with guanidine or with##STR14## wherein each R₃ and R₄ independently have the meanings givenabove.

Preferably, the R₃ amino groups are substituted by not more than onealkyl and, more especially, by no alkyl.

As suitable compounds that may be designated by R₁ -R₃ and from whichthe compounds of formula I can be manufactured by reaction with thediglycidyl ethers or with vinylcyclohexane dioxide, there may bementioned, for example: dihydroxybenzenes such as resorcinol,hydroquinone, pyrocatechol; amino-hydroxybenzenes such as 2-, 3- andespecially 4-aminophenol; thio-hydroxybenzenes such asmonothiopyrocatechol, monothioresorcinol, monothiohydroquinone;hydroxybenzoic acids such as salicylic acid, 3- and 4-hydroxybenzoicacid; amino-benzoic acids such as anthranilic acid, 3- and4-aminobenzoic acid; aminohydroxybenzoic acids such as 3- and4-aminosalicyclic acid, 2- and 4-amino-3-hydroxy-benzoic acids, 2- and3-amino-4-hydroxybenzoic acids; dihydroxybenzoic acid; pyrogallol;aminophenylsulfonic acid; aminoaphthenes, naphthalene diamines; α- andβ-naphtholyquinone and other dihydroxy-naphthalenes; aminonaphthoicacids. There may also be mentioned hydroxypyridines; aminopyridines,dihydroxy-pyridines; hydroxy-aminopyridine; picolinic acid, nicotinicacid, isonicotinic acid, citrazinic acid, amino- and hydroxy-pyridinicacids; aminopyrimidine; aminodihydroxypyrimidines; citric acid;ethylenediamine; guanidine; diaminobutane; bisphenol A. The substitutedbenzenes are especially preferred as starting material.

The compounds R₁ -R₃ that have more than two positions capable ofreaction with epoxide groups are preferred if the coating is to becross-linked as in the preferred embodiment described above. There maybe mentioned especially compounds having at least one amino groupoptionally in addition to other radicals R₃ and their use is thereforealso especially preferred.

In the manufacture of the compounds of formula I, the compounds R₁ -R₃are used with the epoxy compounds preferably in excess, for example in amolar ratio of approximately from 2:1 to 3:1 so that preferably all theepoxy groups react completely, but it is quite possible for a smallerproportion of compounds of formula I that still contain epoxy groups tobe present, especially if in the compound of formula I, X is NH or atleast part of R₃ is NH₂.

The compounds of the formula I and optionally of formula II used in theinvention may, as already explained, be applied preferably as a solutionto the surfaces which will come into contact with the monomers and whichhave previously been thoroughly cleaned. Optionally, this treatment maybe repeated several times after suitable intermediate drying andpossible heating. Normally, however, a single coating is sufficientsince the compounds are distinguished by the ability to adhere well.This treatment is carried out in accordance with the customaryprocesses, for example, by rinsing, spreading or spraying on, or bybriefly flooding the container or the like, preferably by spraying orspreading on, usually prior to each polymerization batch. Preferably,the treated surfaces are then additionally briefly rinsed off with wateror polymerization liquor prior to polymerization with the waste liquidbeing removed.

If the coating of the preferred embodiment is cross-linked, thesubsequent treatment of the container with fresh coatingsolution/dispersion after every polymerization batch is unnecessary.Rather, it is generally then sufficient to remove loose polymer residuefrom the container by rinsing briefly with water. It has proved to be anadvantage to check the container from time to time for damage to thecoating, and optionally, for example after 20 to 70 reaction cycles, toprovide a new coating as a precaution. To prepare the coating, it hasproved advantageous to remove polymer residues and other contaminantsfrom the container. For this purpose, there may be mentioned by way ofexample: mechanical cleaning, treatment with solvents, acids, oxidizingagents and similar substances.

As the effectiveness of the solution or dispersion of the compounds offormula I is not impaired by atmospheric oxygen, no particular attentionneed be paid to excluding air provided that this is not preferred forother reasons, for example to make rinsing with inert gas beforeinitiating polymerization unnecessary.

There are no special requirements as to the surface condition of thepolymerization apparatus, although an undamaged, smooth surface isusually preferred. The apparatus may be made or different materials, forexample glass, enamel or vitreous ware, or metal, especially steel. Theterm "surface" is not restricted to the container wall, but refers alsoto other surfaces coming into contact with constituents of the reactionmixture, for example pipelines, pressure equalizing vessels, valves,baffles, sensors, external reflux condensers, internal condensers,container nozzles and other equipment.

Polymerization itself may, as already explained, be carried out by thecustomary procedures of mass, suspension, emulsion or micro-suspensionprocesses, discontinuously or also optionally continuously, with orwithout the use of seeding preparations, with the customary initiatorsystems, protective colloids, emulsifiers and other polymerizationauxiliaries, optionally under reflux cooling in partially or completelyfilled reaction containers (autoclaves), unpressurized, below, at orabove the autogeneous pressure of the monomers, for example withconcomitant use of ethylene up to, for example, 100 bars or above, withall or individual constituents of the reaction mixture being present orwith part of, or individual constituents of, the reaction mixture beingpresent and part being metered in subsequently, or none of theconstituents being present initially and the constituents being addedaccording to the metering-in process.

Although it is normally superfluous, addition to the polymerizationmixture of a small amount of wall-deposit inhibitor such as citric acidor tartaric acid is naturally not excluded. It is, of course, alsopossible to add dyestuffs which have already been used for this purposeprovided that coloration of the product is acceptable.

The polymers can be worked up in the customary, manner; for example, theresulting suspensions, dispersions or latices or polymers can bedegassed, filtered, coagulated, dried or stabilized in the customarymanner.

It was established that the coating used in the invention, particularlyafter cross-linking, has virtually no further tendency to dissolve orbecome detached so that residues thereof are virtually no longerdetectable either in the product or in the waste liquid.

The following Examples are intended to explain the present invention ingreater detail. They are preferred embodiments of the invention withoutlimiting it strictly. The yields (% of the theoretical value) refer ineach case to the diglycidyl ether used.

EXAMPLE 1

30.4 g (0.22 mole) of 4-hydroxybenzoic acid and 1.0 g of triethylaminein 350 ml of dioxane were introduced into a three-necked flask equippedwith a stirrer, a reflux condenser and a dropping funnel and the mixturewas heated to reflux. While stirring, 34.0 g (0.1 mol) ofbisphenol-A-diglycidyl ether (BD) dissolved in 200 ml of dioxane werethen slowly added dropwise. After completion of the addition, thereaction mixture was maintained at reflux until reaction was completeand then the solvent was removed by distillation. The reaction productwas dried under a high vacuum to obtain a yield of 95.6%.

EXAMPLE 2

30.2 g (0.22 mol) of 4-aminobenzoic acid in 400 ml of ethanol wereintroduced into the same apparatus as in Example 1 and while stirring, asolution of 34.0 g of BD (0.1 mole) in 600 ml of ethanol was addeddropwise. After completion of the addition, the mixture was heated atreflux for a further hour and the solvent was then substantiallydistilled off. Water was added to the residue and the mixture wasacidified and extracted with diethyl ether. The ether was distilled offand the product was dried under a high vacuum to obtain a yield of 95%.

EXAMPLE 3

Analogously to Example 2, 22.0 g of resorcinol (0.22 mole) in the formof its monosodium salt were reacted with 34.0 g (0.1 mole) of BD in atotal of 600 ml of ethanol. After refluxing for three hours, the productwas worked up as described in Example 2 to obtain a yield of 57%.

EXAMPLE 4

Using the procedure of Example 2, 48.0 g (0.44 mole) of 4-aminophenol in1000 ml of ethanol were reacted with 68.0 g of BD (0.2 mole) in 500 mlof ethanol. After reflux for five hours, the solvent was distilled offand the product was dried under a high vacuum to obtain a yield of 97%.

EXAMPLE 5

Using the procedure of Example 4, 10.4 g of 4-aminopyridine (0.11 mole)and 17.0 g of BD (0.05 mole) were reacted in a total of 350 ml ofethanol to obtain a yield of 78%.

EXAMPLE 6

Using the procedure of Example 4, 33.9 g (0.22 mole) of 4-aminosalicylicacid and 34.0 g of BD (0.1 mole) were reacted in a total of 750 ml ofethanol to obtain a yield of 98%.

EXAMPLE 7

20.8 g (0.11 mole) of 2-aminophenol-4-sulfonic acid in 200 ml of ethanolwere introduced into a reaction vessel of Example 1, and the pH wasadjusted to a pH of 8.5 with 2N aqueous NaOH. After heating to reflux, asolution of 17.0 g of BD (0.05 mole) in 150 ml of ethanol was slowlyadded dropwise. After the addition had ended, the reaction mixture wasrefluxed for a further 8 hours and then was concentrated to about 20% bydistilling off the solvent. The residue was diluted with water andacidified. The precipitated product was filtered off and dried under ahigh vacuum to obtain a yield of 62.5%.

EXAMPLE 8

12.1 g (0.11 mole) of 2-amino-3-hydroxypyridine in 250 ml of ethanolwere introduced into the same apparatus of Example 1 and while stirring,a solution of 17.0 g of BD (0.05 mole) in 150 ml of ethanol was addeddropwise. After completion of the addition, the mixture was refluxed fora further 5 hours, and thereafter freed of solvent. Finally, the productwas dried under a high vacuum to obtain a yield of 95%.

EXAMPLE 9

Using the procedure of Example 8, 36.0 g of 4-aminophenol (0.33 mole)were reacted with 30.3 g of butanediol diglycidyl ether (0.15 mole) in atotal of 900 ml of ethanol to obtain a yield of 92%.

EXAMPLE 10

Using the procedure of Example 8, 24.0 g of 4-aminophenol (0.22 mole) in500 ml of toluene and 300 ml of ethanol, and 22.2 g of hydroquinonediglycidyl ether (0.1 mole), which was added dropwise as a solution in250 ml of toluene, were reacted to obtain a yield of 95%.

EXAMPLE 11

15.03 g of ethylene diamine (0.25 mole) dissolved in 250 ml of ethanolwere introduced into a three-necked flask equipped as in Example 1 and asolution of 34.0 g of BD (0.1 mole) in 300 ml of ethanol was slowlyadded thereto at 35° C. After completion of the addition, ethanol andexcess ethylene diamine were distilled off and the reaction product wasdried under a high vacuum to obtain a yield of 94%.

EXAMPLE 12

Example 1 was repeated except that 42.2 g (0.22 mole) of citric acid and1.0 g of triethylamine in 300 ml of dioxane were introduced and 34.0 gof BD (0.1 mole) in 250 ml of dioxane were added dropwise to obtain ayield of 57%.

The following Examples demonstrate the surprising advantages of thepresent invention. Examples 13 to 24, 30 to 32 and ComparisonExperiments A, B, D and E were carried out in a 1 liter steel autoclavefollowing the scheme given below:

(a) Filling the autoclave with tetrahydrofuran (THF), stirring the THFat 60° C. for 16 hours, then discharging the contents by which theabsolute freedom of the vessel from polymer deposits was guaranteed.

(b) Rinsing with acetone.

(c) Cleaning the autoclave with an abrasive agent to ensure that thewalls were free of any residues of earlier coatings.

(d) Rinsing with de-ionized water.

(e) Drying the autoclave at 60° C.

(f) Coating the autoclave and the equipment as given in the individualExamples at room temperature.

(g) Charging the autoclave with a reaction mixture consisting of 200parts by weight of de-ionized water, 100 parts by weight of vinylchloride, 0.16 parts by weight of polyvinyl alcohol having a viscosityof 5 mPas (measured according to Hoppler in a 4% by weight aqueoussolution at 20° C.) and a saponification number of 270 mg KOH/gpolyvinyl alcohol), 0.3 parts by weight of dilauroyl peroxide and 0.1parts by weight of dicetyl peroxydicarbonate.

(h) Polymerization at 59° C. while stirring at 400 rpm until a drop inpressure of approximately 1.5 bars was observed. After discharging theproduct, the autoclave was merely rinsed out with unpressurized water.In this manner, four polymerization cycles in each case were carried outwithout intermediate mechanical or chemical cleaning.

(i) After discharging the fourth batch and spraying out withunpressurized water, the autoclave was treated again as described under(a) with THF. The discharged THF was transferred to a weighed flask anddistilled off. The wall deposit was produced in the flask as a residueand was determined by weighing out. To test the strength of adhesion ofwall deposits, in each case, where specified, also after the fourthbatch, some deposit was scratched off mechanically but not removed fromthe autoclave separately.

Comparison Experiment A

The autoclave was not coated. After polymerization, severe wall depositswere found even after the first batch. After the fourth batch, thecrusts had caked on so firmly that they could be removed mechanicallyusing a spatula only with difficulty. Altogether 10.20 parts by weightwere detached.

EXAMPLE 13

The reactor was coated with a 2% by weight solution of the product ofExample 2 in ethanol which had been adjusted to a pH of 9.5 with 2Nsodium hydroxide solution. The coating was repeated after each batch andafter the fourth batch, the reactor merely showed a light deposit at thetransition region between the liquid phase and gas space, that is, inthe region that becomes exposed by the contraction in volume, or is onlyat times covered by the liquid phase. The minimal deposit could veryeasily be removed with the finger nail and the total wall deposit wasonly 0.70 parts by weight.

EXAMPLE 14

Example 13 was repeated except that the coating solution was adjusted topH 11.0. The entire wall deposit amounted to only 0.13 parts by weightand was therefore scarcely noticeable.

EXAMPLE 15

The reactor was coated before each batch with a 2% by weight solution ofthe product of Example 3 in methanol which had been adjusted to a pH of11.5 with 2N sodium hydroxide solution. The entire wall deposit amountedto only 0.11 parts by weight and was therefore scarcely noticeable.

EXAMPLE 16

The reactor was coated before each batch with a 2% by weight methanolicsolution of the product of Example 4 which which had been adjusted to apH of 12.0 with 2N sodium hydroxide solution. Only at the phase boundaryof the gas space to the liquid phase did a total of 0.10 parts by weightof polymer, easily removable using a finger, become deposited.

EXAMPLE 17

The autoclave was coated before each batch with a 2% by weightmethanolic solution of the product of Example 11 which had been adjustedto a pH of 11.5 with concentrated sodium hydroxide solution. A total of0.30 parts by weight of loosely adhering polymer was detached from thephase boundary.

EXAMPLE 18

The autoclave was coated before each batch with a 4.5% by weightsolution of the product of Example 12 in methanol with a pH of 4.0.Again, a total of only 0.10 parts by weight was detached.

EXAMPLE 19

The autoclave was coated before each batch with a 5% by weightmethanolic solution of the product of Example 1 which had been adjustedto a pH of 12 with 1N sodium hydroxide solution. Altogether, 0.8 partsby weight of wall deposit which was very easy to remove, was dissolvedoff.

EXAMPLE 20

The autoclave was coated before each batch with a 2% by weight ethanolicsolution of the product of Example 11 which had been adjusted to a pH of12 with 2N sodium hydroxide solution. After the fourth batch, an easilyremovable deposit of 0.6 parts by weight had settled only in the regionof the phase boundary.

EXAMPLE 21

Example 16 was repeated with the product of Example 9 and the weight ofthe loose deposit amounted altogether to 0.75 parts by weight.

EXAMPLE 22

Example 16 was repeated with the product of Example 10 and the loosedeposit weighed a total of 0.86 parts by weight.

EXAMPLE 23

From the product of Example 4 and bisphenol-A-diglycidyl ether (BD), a5% by weight solution (molar ratio of the component from Example 4:BD=8:2) was prepared and adjusted to a pH of 12 with 2N sodium hydroxidesolution. Using this solution, the reactor was coated and then heatedfor one hour at 60° C. After the fourth batch, without the coating beingrenewed in between times, the reactor contained a total of 0.45 parts byweight of loosely adhering deposit only at the phase boundary.

EXAMPLE 24

From the products of Examples 3 and 11 and bisphenol-A-diglycidyl ether,a 5% by weight methanolic solution in the molar ratio 8:8:2 of the threecomponents was prepared and it was adjusted to a pH of 11 with 2N sodiumhydroxide solution. After being coated with this solution, the reactorwas heated for 90 minutes at 90° C. After four batches without thecoating being renewed in between times, the reactor contained a total of0.59 parts by weight of loosely adhering deposit only at the phaseboundary.

Comparison Experiment B

In accordance with the general procedure described before Example 13, acopolymer of vinyl chloride and vinyl acetate was prepared in theun-coated autoclave using 200 parts by weight of de-ionized water, 0.6parts by weight of polyvinyl alcohol of a Hoppler viscosity of 25 mPas(a 4% by weight aqueous solution at 20° C.) and saponification number190, 0.6 parts by weight of dilauroyl peroxide, 0.1 parts by weight ofdicetyl peroxydicarbonate, 1.0 parts by weight of trichloroethylene(regulator), 85 parts by weight of vinyl chloride and 15 parts by weightof vinyl acetate.

The autoclave was so encrusted even after one batch that a second batchcould not be polymerized. The very firmly adhering wall deposit wasdissolved off with THF and its weight even after this one batch was 14.3parts by weight.

EXAMPLE 25

With the product of Example 4 and bisphenol-A-diglycidyl ether, a 6% byweight methanolic solution in the molar ratio of 7:3 was prepared andadjusted to a pH 10.5 with sodium hydroxide solution. The autoclave wascoated with this solution and then heated for 1 hour at 90° C.

In accordance with the procedure described before Example 13, acopolymer of vinyl chloride and vinyl acetate was prepared using thecomponents of Comparison Experiment B. Without an interim new coating,four batches were polymerized and the deposit, which did not adherefirmly, weighed a total of 6.90 parts by weight.

The fact that the color and quality of the polymer products was notimpaired in any way should be noted for all those Examples describingpolymerization reactions.

EXAMPLE 26

With the product of Example 4 and bisphenol-A-diglycidyl ether, a 5% byweight ethanolic solution in the molar ratio of 8:2 was prepared andadjusted to a pH of 12 with sodium hydroxide solution. The thoroughlycleaned and completely residue-free inner surfaces and equipment of a 25m³ steel autoclave were coated with this solution and heated for 90minutes at 95° C.

The reactor was then charged in a customary manner with 167 parts byweight of de-ionized water, 100 parts by weight of vinyl chloride, 0.15parts by weight of the polyvinyl alcohol used in Examples 13 to 24 and0.07 parts by weight of dimyristyl peroxydicarbonate, and with stirringthe contents were heated to 56° C. and polymerized. After a drop inpressure of 1 bar, the product was discharged and worked up. Theautoclave was rinsed out with fresh water without being opened andcharged again immediately as above.

After 62 such reaction cycles without being opened in between times orbeing additionally cleaned, the autoclave was opened. Only in thetransition region at the phase boundary and at a few points of theautoclave dome was a slight, not very firmly adhering wall depositfound. However, it was possible to easily remove this without leavingresidues using a high-pressure water jet of about 200 bars.

Comparison Experiment C

A 16 liter stirrer reactor equipped with an anchor mixer and baffle fromwhich polymer had been cleaned completely was used for the preparationof polyvinyl acetate using the following reactants: 100 parts by weightof vinyl acetate, 6 parts by weight of polyvinyl alcohol having aHoppler viscosity of 25 mPas (a 4% by weight aqueous solution at 20° C.)and saponification number of 140, 0.07 parts by weight of hydrogenperoxide as a 20% aqueous solution and 70 parts by weight of de-ionizedwater.

After introducing the water, the polyvinyl alcohol, the H₂ O₂ and 30parts of vinyl acetate, the reactor with its contents was heated to 75°C. with stirring and maintained at this temperature. The remainingmonomer was metered in uniformly over 8 hours. Once metering-in hadfinished, the temperature was increased to 90° C., and polymerization ofthe batch was completed at this temperature over a period of 2 hours.The residual monomer was then distilled off and the reactor was cooledat 20° C. and emptied.

After rinsing the reactor, a firmly adhering encrustation remained onthe wall, stirrer and equipment which could be removed mechanically onlywith difficulty. Further polymerization could not be carried out withoutthorough cleaning in between batches. The wall deposit was 5 parts byweight.

EXAMPLE 27

With the product of Example 4 and bisphenol-A-diglycidyl ether, a 5% byweight ethanolic solution in the molar ratio of 6:4 was prepared andadjusted to a pH of 12 with sodium hydroxide solution. The thoroughlycleaned, completely polymer-free inner surfaces, stirrer and equipmentof the reactor from Comparison Experiment C were coated with thesolution and heated for 120 minutes at 90° C.

Then, as described in Comparison Experiment C, ten polymerizations werecarried out wherein the reactor was rinsed out in between batches withwater only (25 bars pressure). After ten reaction cycles, the reactorwall was completely free from encrustations and only on the stirrer andon the equipment was an easily removable wall deposit detected. The walldeposit after 10 cycles was 2 parts by weight.

Comparison Experiment D

Using the general procedure described before Comparison Experiment A,polystyrene was prepared in the un-coated autoclave from the followingreactants: 400 parts by weight of de-ionized water, 0.45 parts by weightof the polyvinyl alcohol used in Comparison Experiment B, 0.15 parts byweight of methylcellulose MC 25 S, 2.0 parts by weight of dicetylperoxydicarbonate, 1.0 parts by weight of dilauroyl peroxide and 200parts by weight of styrene. The polymerization temperature was 60° C.,the stirrer speed was 300 min⁻¹, (=r.p.m.) and the polymerization timewas 6 hours. After the fourth batch, a firmly adhering wall depositshowed throughout the filled area and had to be dissolved out with THF.Its weight was 4.27 parts by weight.

EXAMPLE 28

With the product of Example 4 and BD, a 5% by weight ethanolic solutionin the molar ratio of 6:4 was prepared, and adjusted to a pH of 12 withsodium hydroxide solution. The autoclave was coated with this solutionand then heated for 2 hours at 90° C. Using the procedure of ComparisonExperiment D without fresh coating between batches, four batches werepolymerized and the resulting very easily removable wall deposit weigheda total of 0.18 parts by weight.

Comparison Experiment E

Comparison Experiment D was repeated except that a mixture of 100 partsby weight of each methyl methacrylate and styrene was used instead ofstyrene. The very firmly adhering wall deposit after four batchesamounted to 1.35 parts by weight.

EXAMPLE 29

Example 28 was repeated except that a mixture of 100 parts by weighteach of styrene and methyl methacrylate was used instead of styrene.After four batches, a slight, very easily removalbe wall deposit of 0.08parts by weight was detected.

Using the procedure described after Example 12, the following threeExamples were carried out:

EXAMPLE 30

The autoclave was coated before each batch with a 5% by weight solutionof the product of Example 7 in an 80:20 mixture of ethanol and waterwith the solution having been adjusted to a pH of 12 with sodiumhydroxide solution. A total of 0.09 parts by weight of wall deposit wasremoved.

EXAMPLE 31

With the products of Examples 4 and 7 (weight ratio 1:1) and BD, a 5% byweight solution in ethanol with 20% water was prepared of a molar ratioof the components of Examples 4 and 7: BD=5:4), and adjusted to a pH of9.5 with 2N NaOH. The reactor was coated with this solution and washeated for 60 minutes at 90° C. After five batches without the coatingbeing renewed in between, 0.3 parts by weight of deposit was found.

EXAMPLE 32

Example 31 was repeated except that the molar ratio of the components ofExamples 4 and 7: BD was adjusted to 1:1 and the solution was adjustedto a pH of 10 with 2N sodium hydroxide solution. After being coated withthis solution, the reactor was heated for 90 minutes at 85° C. Afterfive batches without cleaning in between batches, 0.3 parts by weight ofloosely adhering deposit was produced.

EXAMPLE 33

Using the procedure of Example 2, 85 g (0.78 mole) of 4-aminophenol and21 g (0.11 mole) of 2-aminophenol-4-sulfonic acid dissolved in 800 ml ofethanol and 50 ml of 2N sodium hydroxide solution were reacted with149.6 g (0.44 mole) of BD in 600 ml of ethanol. After eight hours atreflux, the solvent was distilled off and the product was dried under ahigh vacuum to obtain yield of 99%.

EXAMPLE 34

Using the procedure of Example 33, 71 g (0.65 mole) of 4-aminophenol and31 g (0.16 mole) of 2-aminophenol-4-sulfonic acid dissolved in 800 ml ofethanol and 75 ml of 2N sodium hydroxide solution were reacted with136.0 g (0.40 mole) of BD in 600 ml of ethanol to obtain a yield of97.8%.

EXAMPLE 35

Using the procedure of Example 33, 61 g (0.56 mole) of 4-aminophenol and41 g (0.22 mole) of 2-aminophenol-4-sulfonic acid dissolved in 800 ml ofethanol and 100 ml of 2N sodium hydroxide solution were reacted with129.2 g (0.38 mole) of BD in 600 ml of ethanol to obtain a yield of 98%.

EXAMPLE 36

Using the procedure of Example 33, 51 g (0.47 mole) of 4-aminophenol and51 g (0.27 mole) of 2-aminophenol-4-sulfonic acid dissolved in 700 ml ofethanol and 125 ml of 2N sodium hydroxide solution were reacted with122.4 g (0.36 mole) of BD in 600 ml of ethanol to obtain a yield of95.6%.

Various modifications of the process may be made without departing fromthe spirit or scope thereof and it is to be understood that theinvention is intended to be limited only as defined in the appendedclaims.

What we claim is:
 1. A polymerization reactor provided with a coating onthe inner wall of the reactor and other equipment whose surfaces comeinto contact with the constituents of the reaction mixture that at leastsuppresses polymer formation, the coating being comprised of at leastone compound of the formula ##STR15## wherein X is selected from thegroup consisting of --O--, --S--, and ##STR16## Y is selected from thegroup consisting of --CH₂ OR₆ ##STR17## R₁ is selected from the groupconsisting of R₂ --, ##STR18## and R₂ --SO₂ --, R₂ is selected from thegroup consisting of phenyl optionally substituted with at least one R₃and naphthyl optionally substituted with at least one R₃ or aheterocycle optionally substituted with at least one R₃ and derived bysubstitution of nitrogen, sulfur and/or oxygen atoms for at least onecarbon of benzene, cyclopentadiene, indene, naphthylene or theirpartially or completely hydrogenated analogs, an alkyl of 1 to 8 carbonatoms containing at least one R₃, ##STR19## R₃ is selected from thegroup consisting of --OH, --SH, ##STR20## --COOH and --SO₃ H, the R₄ 'sbeing independently selected from the group consisting of hydrogen andalkyl of 1 to 4 carbon atoms, R₅ is selected from the group consistingof ##STR21## R₆ is selected from the group consisting of ##STR22## andR₇ is selected from the group consisting of alkylene of 1 to 8 carbonatoms optionally substituted with at least one alkyl of 1 to 4 carbonatoms, phenylene having at least one R₃ and/or R₄, naphthylene having atleast one R₃ and/or R₄ and ##STR23##
 2. A polymerization reactorprovided with a coating on the inner wall of the reactor that at leastsuppresses polymer formation, the coating being comprised of thereaction product of (A) at least one compound of the formula ##STR24##wherein X is selected from the group consisting of --O--, --S--, and##STR25## Y is selected from the group consisting of --CH₂ OR₆,##STR26## R₁ is selected from the group consisting of R₂ --, ##STR27##and R₂ SO₂ --, R₂ is selected from the group consisting of phenyloptionally substituted with at least one R₃ and naphthyl optionallysubstituted with at least one R₃ and hydrogenated analogs thereof, aheterocycle optionally substituted with at least one R₃ and derived bysubstitution of nitrogen, sulfur and/or oxygen atoms for at least onecarbon of benzene, cyclopentadiene, an alkyl of 1 to 8 carbon atomscontaining at least one R₃, ##STR28## R₃ is selected from the groupconsisting of --OH, --SH, ##STR29## --COOH and --SO₃ H, the R₄ 's beingindependently selected from the group consisting of hydrogen and alkylof 1 to 4 carbon atoms, R₅ is selected from the group consisting of##STR30## R₆ is selected from the group consisting of ##STR31## and R₇is selected from the group consisting of alkylene of 1 to 8 carbon atomsoptionally substituted with at least one R₃ and/or R₄, naphthylenehaving at least one R₃ and/or R₄ and ##STR32## and (B) at least onecompound of the formula ##STR33## wherein R₇ has the above definition ina molar ratio of 10:1 to 1:1.